Inkjet recording apparatus

Abstract

An inkjet recording apparatus for recording an image on a recording medium, including a recording head, a drive circuit and a control device. The head includes an ink passage, a nozzle communicated with the passage, an actuator applying energy to ink in the passage to eject a droplet of the ink from the nozzle onto the medium. The drive circuit outputs a signal for driving the actuator to eject the ink droplet such that at least three ink droplets are ejected for printing one dot. The control device controls operation of the circuit and includes a high-temperature control portion and a low-temperature control portion. The former portion operates, in a first case where an environmental temperature is higher than a threshold, to control the circuit to output a first kind of the signal according to which a dot is formed by a number of ink droplets ejected in series and landing on the medium sequentially in the order of ejection. The latter portion operates, in a second case where the environmental temperature is not higher than the threshold, to control the circuit to output a second kind of the signal according to which a dot is formed by the same number of ink droplets as in the first case. A total ink volume of the droplets ejected according to the second kind signal is smaller than that according to the first kind signal.

1. An inkjet recording apparatus for recording an image on a recording medium, comprising:
 a recording head including:
 an ink passage with ink therein; 
 a nozzle in communication with the ink passage; 
 an actuator which applies energy to the ink in the ink passage to eject a droplet of the ink from the nozzle onto the recording medium; 
 
 a drive circuit which outputs a drive signal for driving the actuator to eject the droplet of the ink, such that at least three droplets of the ink are ejected for printing one dot on the recording medium; and 
 a control device which controls operation of the drive circuit, and includes:
 a high-temperature control portion which operates, in a first case where a temperature of an environment in which the apparatus is situated is higher than a predetermined threshold, to control the drive circuit to output a first kind of the drive signal according to which a dot is formed by a number of droplets of the ink, which are ejected in series and land on the recording medium sequentially in the order in which the droplets have been ejected; and 
 a low-temperature control portion which operates, in a second case where the temperature of the environment is not higher than the predetermined threshold, to control the drive circuit to output a second kind of the drive signal according to which a dot is formed by the same number of droplets of the ink as in the first case, a total ink volume of the droplets ejected according to the second kind of the drive signal being smaller than that according to the first kind of the drive signal. 
 
 
     
     
       2. The apparatus according to  claim 1 , wherein in the second case, a first one and a second one of the droplets coalesce into one droplet after ejected from the nozzle and before landing on the recording medium. 
     
     
       3. The apparatus according to  claim 1 ,
 wherein each of the first and second kinds of the drive signals is formed of a series of pulses including printing pulses each for ejecting a droplet of the ink, 
 wherein the series of pulses forming the first kind of the drive signal further includes cancelling pulses such that a cancelling pulse follows each printing pulse, each of the cancelling pulses being for eliminating a change in ink pressure in the ink passage which is caused by ejection of a droplet of the ink by application of each of the printing pulses, 
 and wherein the series of pulses forming the second kind of the drive signal includes a first printing pulse for ejecting a first one of the droplets and a second printing pulse for ejecting a second one of the droplets, without a cancelling pulse interposed therebetween. 
 
     
     
       4. The apparatus according to  claim 3 , wherein a pulse width of the first printing pulse in the second kind of the drive signal is longer than a pulse width of the second printing pulse in the second kind of the drive signal, and a volume of the second droplet is smaller than that of the first droplet. 
     
     
       5. The apparatus according to  claim 3 ,
 wherein the series of pulses forming the second kind of the drive signal further includes:
 a first cancelling pulse for cancelling a change in the ink pressure in the ink passage caused by ejection of the second droplet; 
 a third printing pulse for ejecting a third one of the droplets; and 
 a second cancelling pulse for cancelling a change in the ink pressure in the ink passage caused by ejection of the third droplet, 
 
 and wherein where A, B, C and D respectively represent an interval between the second printing pulse and the first cancelling pulse, a pulse width of the first cancelling pulse, an interval between the third printing pulse and the second cancelling pulse, and a pulse width of the second cancelling pulse, and T represents a time that a pressure wave generated in the ink in the ink passage takes to propagate along the ink passage one way, A-D are respectively set at values that fall within ranges corresponding to H+ or H in the following tables 1 and 2, in which A-D are represented in units of Ts: 
 
       
         
           
                 
                 
                 
               
                     
                   TABLE 1 
                 
                     
                     
                 
                     
                   A 
                     
                 
                 
                 
                 
                 
                 
                 
               
                     
                   B 
                   2.2 
                   2.3 
                   2.4 
                   2.5 
                 
                     
                     
                 
                     
                   0.3 
                   — 
                   — 
                   L 
                   H 
                 
                     
                   0.4 
                   — 
                   H 
                   H 
                   H 
                 
                     
                   0.5 
                   — 
                   H 
                   H+ 
                   H 
                 
                     
                   0.6 
                   — 
                   H 
                   H 
                   L− 
                 
                     
                   0.7 
                   H 
                   H 
                   L− 
                   — 
                 
                     
                     
                 
             
                
               
               
                
                
               
            
             
                
                
                
                
                
                
                
                
               
            
           
         
       
       
         
           
                 
                 
                 
               
                     
                   TABLE 2 
                 
                     
                     
                 
                     
                   C 
                     
                 
                 
                 
                 
                 
                 
                 
               
                     
                   D 
                   2.2 
                   2.3 
                   2.4 
                   2.5 
                 
                     
                     
                 
                     
                   0.3 
                   H 
                   H+ 
                   H 
                   H 
                 
                     
                   0.4 
                   H 
                   H+ 
                   H 
                   H 
                 
                     
                   0.5 
                   H 
                   H 
                   H 
                   H 
                 
                     
                     
                 
             
                
               
               
                
                
               
            
             
                
                
                
                
                
                
               
            
           
         
       
     
     
       6. The apparatus according to  claim 1 , wherein the total ink volume of droplets of the ink ejected according to the second kind of the drive signal is about 80-90% of the total ink volume of that according to the first kind of the drive signal. 
     
     
       7. The apparatus according to  claim 1 , wherein a print control using the high-temperature control portion and the low-temperature control portion of the control device is implemented when the image to be recorded is a barcode.